Fluid regulators are commonly distributed throughout process control systems to control the pressures of various fluids (e.g., liquids, gasses, etc.). Fluid regulators are typically used to regulate the pressure of a fluid to a substantially constant value. Specifically, a fluid regulator has an inlet that typically receives a supply fluid at a relatively high pressure and provides a relatively lower and substantially constant pressure at an outlet. To regulate the downstream pressure, fluids regulators commonly include a sensing element or diaphragm to sense an outlet pressure in fluid communication with a downstream pressure. Elastomeric diaphragms are cost effective and are typically used with low-pressure applications or non-corrosive process fluids. For high-purity applications, high-pressure applications or highly corrosive process fluids, fluid regulators often employ a metal diaphragm (e.g., a stainless steel diaphragm).
To couple a metal diaphragm to a fluid regulator, conventional fluid regulators clamp a peripheral edge of a metal diaphragm between a regulator valve body and a bonnet. Such a clamped connection localizes deformation and stresses on the metal diaphragm. Further, to provide support to the metal diaphragm, fluid regulators typically employ a back-up plate having a substantially flat or planar contact surface that engages the metal diaphragm. However, some metal diaphragms include convolutions or wave-shaped contours to increase a sensitivity of the diaphragm. A backup plate having a substantially planar contact surface engages a diaphragm having convolutions with a relatively small contact area, thereby increasing stress concentration on the metal diaphragm at the areas of contact. Such localized stress concentrations imparted to the diaphragm can significantly reduce the cycle life or fatigue life of the metal diaphragm, thereby causing increased maintenance and costs.